1、修改序列化的方式

public class JsonLongSerializer extends JsonSerializer<Long> {
    @Override
    public void serialize(Long aLong, 
                          JsonGenerator jsonGenerator, 
                          SerializerProvider serializerProvider) throws IOException {
        jsonGenerator.writeString(Long.toString(aLong));
    }
}

@JsonSerialize(using = JsonLongSerializer.class )
private Long voucherId = null;